The present invention relates to a tubeless pneumatic tire in which air leakage from a puncture in a tread due to running over of a nail and the like can be suppressed and a method of producing the same.
As one of means for preventing generation of air leakage from a puncture portion due to running over of a nail and the like, there is proposed a pneumatic tire having a seal layer in which a puncture sealant for sealing a nail puncture and the like is sealed inside a tread.
Such a tire can be produced by directly coating an inner liner rubber bonded to a molding former with the sealant, then by bonding a carcass ply and a tread rubber to mold a tire raw cover in a raw cover molding step before vulcanization, and by vulcanizing the tire raw cover.
As another method, there is proposed (Japanese Patent Application Laid-open No. 8-323875, for example) a method in which a tire t is vulcanized to form a sack-shaped portion d where inner liner rubber a does not adhere to a sealing rubber sheet b by applying a mold release agent c such as talc between the inner liner rubber a facing a tire inner cavity and the sealing rubber sheet b attached to an inside of the inner liner rubber a and a puncture sealant is injected through an injection hole e communicating with an inside of the sack-shaped portion d by using an injector f after the vulcanization as shown in FIG. 7.
In the former method, however, the step for applying the sealant is troublesome, variations are generated in dimensions of the application, and it is difficult to obtain a uniform seal layer and the uniform tire. In the latter method, because the injection step for injecting the sealant into the sack-shaped portion d after vulcanization of the tire is necessary and a closing step for closing the injection hole e for injecting the sealant is required additionally, a producing process becomes complicated.
The present invention has been accomplished with the above circumstance in view and it is an object of the invention to provide a pneumatic tire having a puncture sealing function which can be produced easily without the above application step and injection step of the sealant and the closing operation of the injection hole and a method of producing the same.
To achieve the above object, a pneumatic tire of the invention has a toroidal shape in which bead portions are connected to sidewall portions extending radially inward from opposite ends of a tread portion and a sealant for preventing a blowout is disposed to extend in a circumferential direction in the tread portion, wherein a seal unit formed by sealing the sealant for preventing the blowout in a sack-shaped member in advance is disposed to extend in the circumferential direction of the tire in the tread portion prior to vulcanization.
A method of producing a pneumatic tire having a toroidal shape in which bead portions are connected to sidewall portions extending radially inward from opposite ends of a tread portion and a sealant for preventing a blowout is disposed to extend in a circumferential direction in the tread portion comprises: an inner liner rubber bonding step for bonding an inner liner rubber onto a molding former; a seal layer forming step for bonding a seal unit formed by sealing the sealant for preventing the blowout in a sack-shaped member in advance to an outer face of the inner liner rubber and forming a seal layer such that the seal layer extends in the circumferential direction of the tire, a carcass ply bonding step for bonding a carcass ply to an outside of the seal unit, a raw cover body forming step for adding other tire main body structure material including bead cores to form a raw cover body; and a vulcanizing step for vulcanizing the raw cover body.